Super-abrasive grain-containing composite material and method of making

ABSTRACT

The invention provides a superabrasive containing composite product, comprising and/or prepared on the intense heating of an SHS process, self-propagating high-temperature synthesis. An effective method of such product is also provided. Said composite comprises a substrate of shaped metallic block and a functional layer of ceramic materials containing superabrasive particles, which is joined on a surface of the former, by means of and intermediated by molten metal which occurred during the SHS process.

TECHNICAL FIELD

This invention relates to a composite comprising wear-resistant materialwith superabrasive particles and ductile metal. Common structuralmetallic materials can be used to make the substrate, which may be ablock in various forms (including plates), and they are prepared eitherthrough a compressive work such as forging, rolling, extrusion andHIPping or by foundry.

BACKGROUND TECHNIQUE

As wear-resistant materials comprising superabrasive particles, diamondor cubic boron nitride compacts are commercially produced mainly inultrahigh pressure processes, and in which the superabrasive particlesare joined immediately with each other or distributed in a ceramicmatrix. While the compacts may be employed as a block of totally uniformstructure, they are more commonly used as a composite with a carbidebacking to which the superabrasive particles are joined during thesintering of the particles themselves. The latter composition is takenmainly as demanded in the subsequent steps of machining into the finalshape or brazing to the support, where a less superabrasive thickness isfavored for a higher efficiency, or a such backing facilitates the work.

However carbide alloy, being a hard and brittle material, cannot fullycomply with the residual stresses which occur at the carbide andsuperabrasive interface after cooled down due to the difference inthermal expansion coefficient. They may eventually cause to disjoint thelayers at a slightest external load.

Further, the use of carbide alloy is not advantageous for the ratherhigh material cost and high specific gravity.

It is known to use a self-propagating high-temperature synthesis (SHS)for the preparation of some types of functional materials. The techniqueis based on the process which occurs with appropriate material systems:a combustion, once initiated by igniting at a spot, sustains itself andpropagates throughout the rest of the material, due to an intenseproduction of heat which spreads and causes a sufficient temperaturerise. It is useful for the production of such compounds as, for example,carbide, nitride, boride, silicide or oxide of the fourth or fifth groupmetals of the periodic table, including Ti, Zr, Ta, Si, as well asintermetallic compounds. This technique is fully described in “Thechemistry of SHS”, published by T.I.C. (1992).

An SHS process, which can produce high temperatures over a short periodof time almost adiabatically, is employed for the formation andsintering, simultaneous or subsequent, of high melting materials and, iftentatively, for the preparation of compact of various materials. Forthe materials, these techniques are available: static compression with amechanical press, instantaneous compression by explosive detonation,isostatic compression with a HIP system, quasi HIP process whereby theformed compact is squeezed from around with a mechanical press in a dieby means of molding sand.

One of the principal objects of the present invention is to eliminatethe above described problems which are associated with conventionalprocesses and products involving an ultrahigh pressure technique, andthereby to provide a heat-resistant product, and also a method foreffectively producing the same, which comprises a metallic layerimproved both in mechanical material strength and thermal stability ofthe joint strength to the ceramic substrate. This has been achievedeffectively on the basis of an SHS technique.

This is an advanced variation of our previous applied invention which isbased on a combined process of SHS with compression and in whichmetallic ingredients are molten with the intense heat of an SHS reactionand allowed to penetrate the skeletal structure of in situ formedceramic material, so that the gaps within and among it are filled in.The product of compact structure exhibits a high resistance to both heatand abrasion that conventional techniques could not achieve.

DISCLOSURE OF INVENTION

The composite of the invention essentially comprises a substrate ofmetallic block and a functional or working layer of ceramic materialwith superabrasive particles, and is characterized by that the latter isjoined to the former on a surface by means of molten metal whichoccurred in the course of the SHS process.

The composite of the invention is effectively produced by:

(1) mixing a composition of powders so formulated as to be capable ofundergoing an SHS process to yield a ceramic product and forming intoone or more pellets, with superabrasive particles being distributed atleast in the region to serve finally as the working surface; (2)arranging the pellet or pellets in the adjacency of said metallic blockto complete the material system, while securing in this system thepresence of metallic material to be molten during the SHS process; (3)causing to initiate said process in said system, whereby said metallicmaterial is molten at least partly as heated by the reaction heat; (4)exert compression with a press in 0.1 to 10 seconds from the completionof the process and holding for 2 seconds at least in order to secure thejoint of the ceramic and metallic bodies.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows the schematic illustration in section of the die used forcarrying out example 1 below;

FIG. 2 shows the schematic illustration in section of the die used forcarrying out example 2;

FIG. 3 shows the schematic illustration in section of the die used forcarrying out example 5;

FIG. 4 shows the schematic illustration in section of the die used forcarrying out example 7; and

FIG. 5 shows the schematic illustration in section of the die used forcarrying out example 10.

PREFERRED EMBODIMENT OF THE INVENTION

Suitable ceramic materials for the skeletal structure include systemscomprising either one or more of carbide, nitride and boride of thefourth to sixth group transition metals of the Periodic Table, and SiC,Si₃N₄, and B₄C. Of those materials carbide, nitride and boride oftitanium or silicon are especially preferred for the cost of production.

It is suggested for achieving a hard and compact composite product touse a starting material comprising both a composition which undergoes anSHS process to yield the hard material and another which provides meltwhen affected by the SHS process. So in the case of the mixture of TiCand Ti—Al, for example, a heat and wear resistant compact matrix can beobtained which comprises a skeletal structure of TiC with the gaps amongand within it filled in with molten Ti—Al. The toughness of the ceramiclayer can be improved by addition of nickel.

In the case of the combination of TiC—Ni and TiB2—Ni, on the hand, atough and wear-resistant product can be obtained due to the formation ofNi and Ni—Ti phases. A wide variety of matrix composition is availablefor the composite of invention according to the use of the final productof compacted composite. Rather a hard product can be obtained from thematerial consisting, for example, of (60 to 90)(Ti or Zr), (3 to 12)(Cor B), (2 to 18)Al, (1 to 5)TiH2, (1 to 7)Cu, and (3 to 20)(Ni or Co) inweight percentage. Or a wear resistant matrix composition can beachieved with the formulation of (60 to 70)(Ti or Zr), (3 to 12)(C orB), (2 to 18)Al, (1 to 15)TiH2, (5 to 25)(Mo or W), (1 to 7)Cu, and (3to 20)(Ni or Co).

Common structural materials of ductile metal are employed for formingthe substrate of the invention; appropriate material composition andsize are selected to well match the fixture and post-treatment incorrespondence with the particular end use.

The composite and metallic sections are bonded in a similar way to thewelding. The short duration, of the order of a few seconds, of heatgeneration and use of metallic substrate effective for heat radiationonly gives a limited zone in which melting or diffusion occurs, so theessential properties of the bulk of substrate metal remains leastaffected by such intense heat. Thus a substrate of hardened steel, forexample, will be only affected and reduce in hardness in the adjacencyof the joint, while the bulk of the functional structural body remainsunaffected in properties. The substrate may be made of various grades ofsteel for common uses. SUS stainless steel (JIS) and copper also may beused for higher resistance to corrosion or weather, while titanium oraluminum based materials are preferred for a lighter construction. Assome combinations of substrate metal and ceramic material may suffercracking due to the difference in coefficient of thermal expansion atthe interface of the materials, a transition layer of compacted powderof intermediate composition may be inserted between the two materials,forming as a whole an inclined functional material. The intermediatelayer, as necessary, may consist of several sublayers; they are eachmade as a pellet, or compacted powder mixture, of stepwise varyingcompositions and the necessary number of them are arranged in stackbetween the functional and supporting bodies for the use as a startingmaterial.

The short heating duration, of the order of a few seconds, in the SHSprocess does not allow a long distance of flow of melt for filling thegaps within and around the skeletal structures. So it is important forthe purpose of forming an adequate stress relieving layer to vary thecomposition so that the proportion of metallic components relative tothe ceramic materials is decreased in steps from the substrate endtowards the ceramic functional end, thereby minimizing the discontinuityin resulting structure.

The metallic material for bonding the substrate metal to the ceramiclayer should exhibit good tensile and bending strength, in addition torather a high melting point. So nickel in particular is suitable; theTiC/Ni and TiB2/Ni are especially good as a heat resistant for commonpurposes, while SiC/Ni and Si3N4/Ni are suitable as a heat resistantmaterial when used in an oxidizing atmosphere.

On the other hand, the combination of TiB2/Si is effective for achievinga wear resistance on the metallic surface, even if with rather a lowtoughness: a comparative abrasion test indicates an abrasion resistanceresult with this compound more than 100 times that of carbide alloy.

The synthesis of ceramic material is possible with the heat productionby the SHS process of starting materials alone, by using a compositionor combination to achieve a high adiabatic combustion temperature.Adequate combinations include, for example, a powder mixture of titaniumor zirconium with carbon or boron, or nitride powder of silicon,titanium or zirconium with nitrogen (from the atmosphere).

Some functional layer compositions, however, may be insufficient in heatproduction for completing the process.

A chemical oven of formulated powder mixture is arranged in adjacencywith the starting materials in order to make up and secure the heatrequirement if they yield only a heat amount insufficient for sustainingthe process, due to the functional layer composition intended.

When arranged in separation from the pellet of synthesis startingmaterial, the widely used traditional combination of aluminum-iron oxideis also available for the chemical oven. This arrangement, however,yields molten iron, which tends to weld the product. Such problem can beavoided by using the Ti—C system, which does not involve liquid relatedtroubles by quickly yielding the TiC product in solid form, while themass of chemical oven products conveniently serves also as a compressionmedium at high temperatures. The chemical oven is also effective as acooling retarder and minimizes cracking of the composite product due tothe thermal deformation.

The chemical oven is also available for welding an unexothermic orinsufficient heat generating composition of starting materials, in sheetor grains, to the substrate. For this purpose, heat resistant parts canbe produced with a TiC or TiB based porous ceramic sheet joined to anSUS stainless steel substrate, by using a pellet or compacted nickelfoil or powder mixture of Ti or Ni with C or B, as inserted at theinterface between the functional layer of TiC or TiB based porousceramic sheet and SUS stainless steel substrate.

Similarly, wear resistant products can be produced from a superabrasivecontaining mixture of WC—Co or WC—Ni powder, as formed, green fired orsintered, by heating from around with a chemical oven; in the productthe functional layer skeletal structure consists of WC particles whichare bonded together and as a whole to the substrate with Co or Ni.

Thus the use as a bonding medium of the melt occurring during the SHSprocess allows a joint of significantly improved strength over thetraditional brazing and even comparable with the technique with fusedmetal under ultrahigh pressure at an elevated temperature. So the listof component groups available for the pellet of the present inventioncan be summarized as: (Ti, Zr, Hf, Si, Mo, W, Ta, Nb, Cr)—(C, B, N)—(Si,Ni, Co, Cu, Al), and the preferred combinations include: TiC—Ni,TiB2—Si, TiB2—Ni, SiC—Ni, Si3N4—Ni.

Diamond particles, as superabrasive contained in the wear resistantlayer, can transform to graphite when exposed to the high temperatureduring the process. The graphite on the diamond surface decreases thestrength of joint to the ceramic body and also the wear resistance. Therate of graphitization process is more dependent on the duration of theintense heat than the magnitude itself of the latter, so in the SHSprocess whereby diamond is subjected to the high temperature for a fewseconds, graphitization damage is practically negligible for a size over10 μm.

In case of possible damage to the superabrasive particles contained inthe functional layer due to the excessive heat generation during the SHSprocess, the addition of neutral, stable compound as a diluent is alsoeffective, such as carbide, nitride, boride and oxide, premixed in theceramic starting materials

For a functional layer with diamond particles, an additive to yieldhydrogen during the process, such as TiH2, may be advantageously used inthe matrix, in order to prevent the deterioration of diamond bygraphitization, which oxygen promotes. As an ingredient neutral to theprocess, they should be used in specific proportion; an amount of 0.2 to15 weight % is appropriate, with the preferred range being between 1 and5%.

While it may be desired that for the use as a wear resistant materialthe functional layer surface be covered totally with superabrasiveparticles, the diamond content in the surface should not exceed anyway80% by volume, in consideration of the retention to be secured by thematrix. The lower limit is advantageously set between 25 and 60%, with afair performance at 10%, though.

For the superabrasive particles used in the ceramic body, retention ofdiamond particles to the matrix can be effectively improved with acoating on the surface. Good results are achieved with a coating oftransition metal of group IV, V, and VI in the Periodical Table,including Ti, Cr, Mo and W, as well as their carbide, nitride, andboride. Traditional techniques are available to deposit the coating,such as vapor deposition, CVD, and dipping for the transition metal. Afirm joint is created between the coated metal and superabrasivesubstrate by means of their compound which is formed at least partlyfrom the ingredients at the interface, in the SHS high temperaturecondition during the preparation of the tool material.

With the coating being effective for protecting the superabrasivesubstrate from the intense heat and abrupt temperature change, a widervariation of matrix compositions is available by allowing to produceextremely high temperature over 2000° C. The coating also serves as abarrier against the atmospheric oxygen and impedes its contact andresulting promotion of graphitization.

For wear resistant products prepared in an SHS process, it is oftendemanded that the functional surface alone have such property, while thebulk body including the substrate exhibit a good machinability preciselyto the specification given, so the construction with a monolayer ofsuperabrasive particles on the functional surface alone is sufficientfor most cases of application. For applications as a tool material, suchdesign, however, achieves rather short tool life, for a demerit.Overcoming this problem, a machinable wear resistant product ofsufficient thickness can be obtained by forming a wear resistantfunctional layer, with superabrasive particles distributed throughoutthe bulk of matrix, while a backing is made of the same material as saidmatrix (but without superabrasive particles) and is arrangedcontiguously between the functional layer and substrate, in support ofthe former.

In the invention the starting material is conveniently and normallycompacted into a pellet before it is loaded in the reactor. Since theproduct is often hard and, in particular, the superabrasive containinglayer is almost impossible to machine, the pellets should be designedand molded into the final form as closely as possible, taking intoconsideration the shrinkage during the sintering process. In theproduction of wheel forming dresser of TiB based matrix scattered withdiamond particles, for example, the pellet is prepared either by formingin the die with a cavity of final product dimensions or first forminginto a cylindrical or prismatic pellet, which is then machined to thefinal shape before it is subjected to the SHS process. In the case ofthe former, a pellet may be prepared with diamond particles deposited onthe working surface alone, by spreading them in the die cavity areacorresponding to the working surface, or by fixing them with adhesive inadvance, then filling the matrix ingredient materials, and pressing intothe form.

As the preparation of a wear resistant product with curved surfacestakes steps of placing pellets of starting materials contiguously inadjacency with- and exerting a pressure onto such curved substrate,isotropic compression can be achieved to a degree by using molding sandas a compression medium.

The use of molding sand is also effective for forming a wear resistantlining on the inside surface of a pipe or a valve. In such working withhollow parts the substrate is available as a pressure vessel, and alarge temperature gradient may be provided between the substrate andfunctional layer, by cooling the outside surface of the substrate bynatural or forced ventilation.

Ceramic materials in general show good resistance to compression butpoor to tension. For the composite produced by the invention, however,the functional layer is under compression at room temperature, due tothe smaller coefficient of thermal expansion with the functional layerthan with the metallic substrate, as confirmed by the observation of thelattice parameter for the metallic phase in the ceramic body at- and inthe adjacency of the interface. Further the use as a heat resistantmaterial may usually hold the ceramic side towards the highertemperatures and thereby in compression favorably. Special care shouldbe taken, however, in the designing of a product of blocky form, so asto secure that the functional layer side be steadily in compression.

The density of a pellet as formed should not exceed 75% the theoreticalvalue for use in a process in which the temperature rise, necessary forthe sintering, is essentially achieved by the chemical reaction withinthe pellet, while the pellet should be compressed as densely as possibleby means of CIP or any other technique available, for a process wherethe necessary heat is basically supplied from a chemical oven outsidethe pellet.

The formed pellet is mounted on a compression system, which is equipedwith an igniter (that is a graphite or metallic heater, for example).For the compression system available are such known techniques as diepress, hot press system or HIP system.

A system with a closed work chamber can be conveniently adapted to thepreparation of a nitride based matrix in a nitrogen atmosphere, morecompact product by securing in a vacuum the removal of gas which mayevolve during the process, or product with minimized deterioration ofdiamond or matrix due to oxidation by treating in a hydrogen atmosphere.

A piece of insulator should be conveniently inserted between the pelletand die, in order to maintain the process temperature and at the sametime for the protection against the deformation or damage to the die,although a hot pellet may be compressed immediately in someapplications.

Molding sand, as filled and pressed around a pellet, serves as insulatorand good pressure medium, as well, to give a quasi-isotropiccompression. This is especially useful in the production of blocky formproducts.

With a hot press system, matrix compositions of insufficient heatgeneration also can be processed by properly operating the attachedheating system. The latter is also available as an igniter.

When a HIP system is used for compression of the pellet, the latter isformed densely, enclosed hermetically, degassed and sealed, andsubjected to the process in an arrangement with an SHS heating mixture(that is chemical oven) around. The attached heating system is alsoavailable as an auxiliary heater or igniter.

When necessary, a tool support blank may be placed together with thepellet for joining. For example, a round rod tip of steel, as a segmentof drill shank blank, may be placed in the die together with a formedpellet which is surrounded by a chemical oven composition, so thecomposite compact may be welded to the substrate of steel at the sametime as it is is formed. This technique causes no essential damage tothe property of the hardended steel substrate as the intense heatgeneration takes place in a restricted zone which moves. As demanded, acooling system also may be arranged on the back side of the metallicsubstrate, so that a large temperature difference is provided there fromthe site of reaction and, thereby, the essential properties of thesubstrate material is secured, while the functional layer is imparted ofresistance to heat or wear.

The pellet, loaded in the system, is ignited to initiate the SHS processunder no or slight compression. An easy burning powder mixture may beinserted between the pellet and heater for facilitating to induce theburning of the pellet. A pressure of suitably 10 to 200 MPa is held for2 to 150 seconds and, preferably 2 to 60 seconds, by startingimmediately after the combustion flame has reached the other end of thepellet and the latter as a whole is heated at a sufficiently hightemperature (or within 0.1 to 10 seconds of the termination ofcombustion).

The composite material obtained by the invention had a superabrasivecontaining ceramic layer which is firmly joined to the substrate ofcommon metallic material, with the joint comparable with that achievedin the ultrahigh pressure high temperature technique. So they can besuccessfully employed in various uses, as a planar wear resistant partsincluding sliding plates, bearing components and surface plate, or as ablocky wear resistant parts including nozzle, bent pipe lining, and diecore, as well as various grinding and cutting tools and wheel tips.

In the composite products of the invention, when a hot press techniqueis utilized, the superabrasive containing ceramic material in thefunctional layer is joined and welded to the metallic substrate duringthe synthesis and compaction of the ceramic product, a firm joint orwelding is achieved at the interface by the co-melting of certainfunctional layer components and metallic substrate components and,thereby, forming a single integrated structure. Further thecharacteristic limited heating zone of the SHS process results only inminimum thermally affected zone, so the often demanded properties oftoughness, good workability and light weight can be secured.

While residual stresses have raised a serious problem to a compositeproduct prepared under an ultrahigh pressure technique, they can bemoderated now by using a lower hardness metal become now available.

An improvement can be achieved by the invention in material weight andcost, and that no or little work is necessary with the substrate.

In short, the present invention, based on the combined techniques of theSHS and various compaction, allows to prepare a diamond containing toolor construction parts of essentially increased dimensions overconventional techniques with ultrahigh pressure.

EXAMPLE 1

A starting material was prepared from 1:1 mixed powder of 22 μm (nominalsize; effective and saved hereinafter unless otherwise indicated)titanium and 7 μm carbon, by adding 25 wt % nickel powder (under 300mesh). It is then formed in a die into a square pellet of 100×100×5 mm.

Another dose of mixed powder of starting material composition wasadmixed with 30% by volume of 20/30 μm diamond powder and compressedinto a second pellet of the same dimensions. The arrangement shown inFIG. 1 was used for further operation.

In the die 11 first placed a 100×100×3 mm wide SUS stainless steel plate12, then the first formed pellet 13 and at the top the second pellet 14.

Over the assembly spread was 30 grams of 1:1 (in molecular ratio) mixedpowder of Ti and C as an igniting medium 15 and a graphite heater 16.The space between said assembly and die 11 was filled with molding sand17; a punch 19 was laid over it with an insulator sheet of ceramic 18.The graphite heater 16 was turned on to ignite the specimen; 2 secondsafter the termination of combustion, the punch 19 was driven to exert apressure of 100 MPa to the specimen and held for 30 seconds. Theresulting product was a fine structured ceramic body joined firmly tothe SUS plate, the former composed of a skeletal structure of TiC withthe gaps around it filled mainly with Ni as well as Ti—Ni intermetallicalloy; it was used successfully as a wear-resistant tile.

EXAMPLE 2

An excavator edge was tentatively prepared. Powders of 22 μm Ti, 7 μmcarbon and under 325 mesh Al were dosed in a Ti:C:Al proportion byweight of 73:11:16 (16) and mixed well to prepare the matrix startingmaterial. The latter was admixed with 1 wt % of TiH2 and further with 25volume % of 40/60 μm diamond particles, mixed fully and formed in a dieat a pressure of 10 Mpa into truncated conical pellet which measured 40mm across at the base and 10 mm thick, with a point angle of 120 degree.

The arrangement shown in FIG. 2 was used, in which the die set 21comprised a core 22 with a bore 40 mm across and 65 mm long, and a punch23. A sleeve 24 of sintered mullite is fitted inside the core 22. Asupport member of SUS stainless steel 25, conically pointed at an angleof 120 degrees was set in the core 21 at the bottom, then the pellet 26was placed over it. Over the pellet, 30 grams of 1:1 Ti—C mixed powder27 was loaded and graded, then came an igniter of graphite ribbon 28,which was covered with molding sand 29 to a thickness of 20 mm. Thepunch 23 was set at the top. A thermocouple (not shown) was so arrangedas to be in contact with the bottom of the pellet through the 2 mmacross axial hole provided at the center of the support member.

The ready assembly of die set was mounted on a monoaxial hydraulicpress, and current was passed to the graphite ribbon to ignite thepellet without dreiving the press. When a temperature of 1800 degrees C.was attained at the pellet bottom, the press was operated to quicklycompress the work and hold a pressure of about 100 Mpa for 40 seconds.The recorded cycle parameters indicated that the compression startedabout 0.5 second after the termination of combustion.

The recovered product exhibited metallic luster in the matrix region,which was analyzed by XRD to consist of TiC and TiAl. Optical microscopyin the ground area showed a uniform distribution of diamond particles inthe matrix, while XRD indicated no trace of graphite formation on thesurface of diamond particles.

EXAMPLE 3

The functional layer material was composed of 80Ti/20B mixed powder,which was further admixed with 33 vol. % of 12/25 μm diamond particles.The die with a 75 mm across cylindrical cavity was loaded of a 10 mmthick SUS plate at the bottom, then a 0.5 mm thick Ni sheet, over which40 grams of Ti—B mixed powder with diamond particles was spread andgraded. Then came 25 grams of of 1:1 (in molecular ratio) Ti—C mixedpowder as a chemical oven at the top.

Further a graphite igniter was placed; it was covered with a 10 mm thicklayer of molding sand, on which the upper punch was arranged.

The process temperature was monitored by means of a thermocouple whichwas set in the through hole provided in the SUS plate at the center,while the heating and compression was conducted as in example 1.

The product was a wear resistant composite body of 2 mm thick TiB layerdeposited on the SUS steel plate, and EPMA conducted on the productsection showed a 1 mm wide gradient in Ni concentration from theinterface to the working surface, and indicated the contribution of Nito the bonding within the layer of TiB and as a whole to the substratemember.

The recovered product was wire-cut and ground at the tip to be used as acutting tool edge for wood machining.

EXAMPLE 4

A mixed powder of 65Ti/11B/4Cu/19Ni/1TiH2 (wt %) was used for thematerial of functional layer. 40 vol. % of this powder was admixed with60 vol. % of 0.5 μm thick Ti coated 30/40 μm diamond particles and fullymixed, and formed into a pellet 98 mm across and 2 mm thick. It wasplaced on an SK carbon steel plate 98 mm across and 5 mm thick, andtogether put in a die cavity 100 mm across lined with mullite ceramic,over which 1:1 Ti—C mixed powder was spread to a thickness of about 10mm as an igniting medium for facilitating the ignition, and further agraphite igniter. The operation of example 1 was repeated from ignitionto compression. The product was cut and polished before it was used as amachine tool.

EXAMPLE 5

The die arrangement as schematically illustrated in FIG. 3 was usedwhich comprised an encasement 30 with a bore 100 mm across and a punch31, and a mullite sleeve 32 was tightly fitted inside the encasement. Acircular saw blade blank 33 of 75 mm diameter and 1 mm thickness wasplaced in it with a 65 mm across, 15 mm thick cylindrical block of steel341, 342 on each side, for the purpose of heat radiation from andprevention of deformation of said blade blank during the SHS process. Onthe work table 35 the assembly was placed as supported from below withsprings 361, 362 inside the ceramic receiver ring 37, with a ceramicsheet 38 laid over on the upper block 342 for heat insulation. Saidblank 33 was surrounded with a 5 mm across, 3 mm thick annular pellet39, which comprised for composing the matrix mixed powder of60Ti/10C/10Al/3TiH2/5W/5Cu/7Ni (in wt %), admixed with 20% of coateddiamond particles (in particular, 120/150 μm substrate diamond particlescoated with 2 μm thick Mo deposit). The space around the cylindricalwall of the pellet 39 was filled with equimolar mixed powder 40 of Tiand C as a chemical oven material. The remaining space was filled ofmolding sand 42, while a heater 41 was arranged in adjacency with themixed powder 40 at an end. Compression was started about one secondafter the termination of combustion, and a pressure of 100 MPa wasexerted on the pellet for 30 seconds. The product was effective as ablade for cutting ceramic blocks.

EXAMPLE 6

Diamond powder, coated with 2 μm thick Mo and 1 μm thick Cu inside andoutside layers on the 120/150 mesh substrate was provided, and 15 vol %of it was admixed to the metallic powder of matrix composition of65Ti/23Co/12Al (in wt. %), and formed into a truncated conical pellet of10 mm tip diameter, 20 mm base diameter and 15 mm thickness. It wasplaced in the 40 mm across die bore in abutment to an SK steel round rodof 17.5 mm diameter at one, surrounded by a 5 mm, approximately, thicklayer of 1:1 Ti/C mixed powder for inducing burning, and filled withmolding sand after the arrangement of the ignition heater. The die wasplaced in a hermetic container and the inside space was degassed andthen filled with nitrogen; after that the process was initiated byigniting. Compression was started 4 seconds after the ignition, and apressure of 100 MPa was held over the pellet for 20 seconds. The producthad a construction of matrix which comprised a functional layer joinedfirmly to a substrate of SK steel, with the former comprising diamondparticles distributed and secured in the matrix of TiN, TiAl, TiCo orthe like, and was used as a dresser.

EXAMPLE 7

70:30 (wt. %) mixed powder of under 20 μm Ni/Al was used for the matrixcomposition. The superabrasive was 0.2 μm thick W coated 6/8 μm diamondparticles. 20 vol. % of it was admixed to said matrix composition andformed into a first pellet of 150 mm O.D., 100 mm I.D., and 5 mmthickness, while the pure matrix composition without superabrasivecontent was formed into a second pellet of the same O.D. and I.D. but 8mm thickness. The die arrangement of FIG. 4 was used to prepare a type6A2 cup wheel with a silumin blank.

On the work table 43, as shown in FIG. 4, a wheel was prepared using a155 mm bore die encasement 44. With the bore lined with a 2 mm thickceramic sheet 45 for heat insulation, the inside space was filled with,from bottom to top, wheel blank 46 and, in alignment with said sleeve47, the second pellet 48, and the first pellet with diamond particles49. Further a 3 mm thick layer of 1:1 (in molecular ratio) mixed Ti/Cpowder 50 of was laid, an ignition heater 51 was arranged, and 20 mmthick layer of molding sand 52 laid. Compression was exerted one secondafter the ignition, and a pressure of 50 MPa was maintained for 20seconds.

The product, with a NiAl matrix in which diamond particles were firmlyheld and distributed up to a depth of an approximate 3 mm in the surfaceregion, was used effectively in a lapping wheel.

EXAMPLE 8

Mixed powder of 60Ti/20B/20Ni (in wt %) was used for composing thematrix. 20 vol. % of coated diamond particles, with 40/60 μm diamonddeposited with 4:6 (in wt %) W—Mo alloy, was admixed to said mixedpowder for the matrix, and formed into a circular pellet of 50 mmdiameter and 10 mm thickness. The substrate was a circular copper plate50 mm across and 10 mm thick, while a 0.5 mm thick nickel sheet wasinserted between the substrate and pellet. The steps to follow wereconducted as in example 3, with a corresponding die and materialarrangement.

The product showed a matrix of TiB, TiB2 and TiNi, holding firmlydiamond particles, and joined well as a whole to the copper substrate.

EXAMPLE 9

A 73:11:16, in weight ratio, mixed powder of Ti, graphite and Al, wasprepared by using the same set of materials as in example 2 for thematrix. This powder was further mixed with 80/100 μm cubic boron nitrideparticles, deposited with 2 μm thick Mo layer at a volume ratio of 1:1,and formed into a circular pellet of 30 mm diameter and 5 mm thickness.The sintering process was conducted in a 50 mm bore die, by using a 3 mmthick SK steel plate for the substrate, while a 0.2 mm thick Ni sheetwas inserted between the pellet and substrate. Such pellet was placed inthe die, as surrounded by a 10 mm thick layer of 1:1 Ti/C mixed powderas a chemical oven composition. Compression was started at the time atemperature of 2000 degrees C. was attained at the pellet bottom, and apressure of 80 MPa was maintained for 30 seconds. The product recoveredwas cut and machined into a tool tip and used for grinding steel works.

EXAMPLE 10

35:65 (in weight ratio) Ti/Ni mixed powder was formed into a 10 mm thickcylindrical first pellet 55 and placed in the 50 mm I.D. and 50 mmlength bore of a cup-shaped copper die 54 in a peripheral abutment tothe wall, as schematically shown in FIG. 5. Both another hollowcylindrical pellet 561, with 30 mm O.D., 15 mm I.D. and 40 mm length anda solid cylindrical pellet of 30 mm O.D. and 10 mm thickness 562 wereformed by composing of 40 vol. % 30/40 μm diamond particles and thebalance of 70:30 (by weight) Ti/B mixture, and were arranged as a set ofsecond pellets 56 in the peripheral abutment inside the first pellet 55.The space inside said second pellets 56 was filled with 80:20 Ti/Cchemical oven composition 57, with a graphite heater 58 arrangedproperly. A punch of alumina 59 was used for the compression after theprocess. The product as recovered was ground on the inside surface andused as a sample nozzle for a water jet machine.

EXAMPLE 11

A twist drill blank of 30 mm diameter and 60 mm length was prepared from88WC-12Co carbide alloy, with a groove 8 mm wide and 5 mm deep forformed on the site of edge. An 0.1 mm thick Ta sheet was wrapped aroundsaid blank, and held vertical in an alumina tube along the 60 mm boreaxis. Said groove was filled with 70:30 (by weight) Ti/B mixed powder,admixed with 45 vol. % 30/40 μm diamond particles, while the spacedefined by the Ta sheet and alumina tube wall was filled with 80:20 Ti/Cmixed powder, as a chemical oven composition.

A graphite heater was arranged at one end of the Ti/C mixture, and thewhole was placed in a pressure resistant vessel of 120 mm I.D. and 180mm height, which then was degassed. Nitrogen was introduced 5 secondsafter the ignition from the cylinder source that was directly connectedwith said vessel, and filled to a pressure of 10 MPa.

The product, with a recess occurring at the groove, was ground with acenterless grinder to an O.D. of the carbide of 22.5 mm, then an edgewas was created.

EXAMPLE 12

A circular plate 125 mm across was prepared by using the materials andconditions specified in Table 1 below at run numbers 1 to 12, for theuse as a wear resistant material or tool blank. In each case, a die of200 mm I.D. was used, with a 5 mm, approximately, thick superabrasivecontaining matrix layer and a 10 mm thick substrate. The powder sizesused were 22 μm for Ti, 7 μm for C and under 300 mesh for the others.The intermediate zone refers to a matrix portion without superabrasiveparticles. The thickness of chemical oven layer was approximatelyconstant at 10 mm. The compression was a quasi-isotropic, as conductedby means of molding sand, and started 5 seconds after the ignition,while a pressure of 5 MPa was maintained for 30 seconds.

TABLE 1 superabrasive transition adhesive layer run matrix compositioncontent layer thick- chemical process no. (weight ratio) material sizeμm vol % thickness nature ness substrate oven atmosphere 1 18Ti—69W—13Bdiamond 12/25 30% 2.0 mm Ni plate 0.5t SK* steel TiB vacuum 227Ti—54Mo—19B cBN 20/30 40% — Ni pellet 1.0t SUS* steel Ti:B 3 94W—6Cdiamond  8/16 surface layer — — Ni plate Ti:C 70% 4 70Ti—10Al—20B cBN30/40 25% 1.5 mm — silumin — vacuum 5 50Ti—30Si—20B cBN  8/16 30% — Niplate 0.5t Ti — Ar 6 42Mo—43Zr—15B diamond  8/16 20% 2.0 mm Ni plate0.5t SK* steel — Ar 7 50Al—50Ti diamond 12/25 25% 2.0 mm Ni—Al pelletSUS* steel — N₂ 8 Si diamond 4/8 20% — Ni plate 0.5t Cu — N₂ 9 60Ti—40TacBN 4/8 25% — Al plate 1.0t Ni — N₂ 10 80Ti—20Ni diamond 20/30 30% 2.0mm — SK* steel — N₂ 11 50Si—50B diamond 4/8 20% — Ni plate 0.5t SK*steel — N₂ 12 Ti—Si diamond 12/25 35% — — Ni plate N₂ *Designationaccording to the Japanese Industrial Standards

Industrial Applicability

The composite material of the invention can be employed in various usesas a planar wear resistant material, including sliding plates, bearingparts and surface plate, or blocky wear resistant parts such as nozzle,bent pipe lining and die core, as well as abrasive tips for varioustypes of tools.

What is claimed is:
 1. A superabrasive containing composite, comprising:layers of a substrate portion of shaped metallic block and a functionalportion of ceramic material which comprises a working surface containingsuperabrasive particles, the latter layer being joined on a surface ofsaid substrate by means of molten metal which occurred during an SHSprocess, and said ceramic material forming a skeletal structure andcomprising a carbide, nitride, carbon-nitride, boride, or silicide of agroup IV transition metal or aluminum, boron carbide, or a mixturethereof, and a metallic material filling the gaps within and among saidskeletal structure.
 2. The composite as claimed in claim 1, in whichsaid ceramic material is a product formed in situ by a self propagatinghigh temperature synthesis (SHS) process.
 3. The composite as claimed inclaim 1, in which said molten metal comprises as the basic component atleast one selected from iron group metals, copper, aluminum andtransition metals.
 4. The composite as claimed in claim 1, in which saidfunctional portion has a matrix which essentially consists of ceramicmaterials.
 5. The composite as claimed in claim 1, in which said ceramicportion comprises the structural and filling materials at a proportionwhich varies from the working surface to the substrate interfacecontinuously or in steps.
 6. The composite as claimed in claim 1, inwhich said functional portion has a thickness of 0.5 to 20 mm.
 7. Thecomposite as claimed in claim 1, in which said superabrasive particlesare distributed at least on the surface of said ceramic layer.
 8. Amethod of producing a superabrasive containing composite, comprising:(1) forming a powder mixture that is capable of undergoing an SHSprocess to yield a ceramic product into one or more pellets, whileadmixing superabrasive particles into said powder mixture at least in anarea which will serve as a working surface, (2) placing said pellet orpellets in the adjacency of a substrate of a shaped metallic block toprovide a starting material system, while securing in said system afirst chemical composition with a metallic component which is capable ofmelting during the SHS process, (3) initiating the SHS process withinsaid system and thereby heating and melting at least partly saidmetallic component, and (4) exerting a pressure with a press by startingwithin 0.1 to 10 seconds of the termination of the process and holdingfor at least 2 seconds and thereby joining the in situ formed ceramicproduct and said metallic block.
 9. The method as claimed in claim 8, inwhich a second chemical composition capable of undergoing an SHS processis arranged separately from but in adjacency with said pellet andmetallic block, and the heat of melting said metallic component issupplied at least partly by the SHS process of said second chemicalcomposition.
 10. The method as claimed in claim 8, in which the heat ofmelting said metallic component is supplied totally by the SHS processwithin said pellet.
 11. The method as claimed in claim 8, in which saidceramic material comprises at least one selected from carbide, nitride,carbo-nitride, boride, silicide of a group IV to VI transition metal andaluminum, and boron carbide.
 12. The method as claimed in claim 8, inwhich said metallic component is used in powder, mixed with the ceramicforming materials and distributed in the pellet.
 13. The method asclaimed in claim 8, in which said metallic component is formed and usedas a second pellet and arranged between the first pellet of ceramicforming powder mixture and said metallic block.
 14. The method asclaimed in claim 8, in which said metallic component is formed and usedas a sheet and arranged between at least one pellet of ceramic formingmaterial powder mixture and said metallic block.
 15. The method asclaimed in claim 8, in which said metallic component is yielded in andsupplied from said substrate during the SHS process.
 16. The method asclaimed in claim 8, in which said metallic component comprises at leastone selected from iron, copper, aluminum and transition metals.
 17. Themethod as claimed in claim 8, in which said powder mixture comprises atleast one metal of titanium and silicon, and/or one refractory substanceselected from their carbide, nitride and boride.
 18. The method asclaimed in claim 8, in which said compression technique is one selectedfrom direct compression in a die, quasi-isotropic compression withpressure medium and roll pressing.
 19. The method as claimed in claim18, in which said pressure medium comprises molding sand.
 20. The methodas claimed in claim 18, in which said pressure medium comprises theproduct of the SHS process.